The present invention generally relates to valves. More particularly, this invention relates to 3-way poppet style valves utilizing valve stems to control the flow of fluid between a common port and two other ports.
Various types of valves are used in the semiconductor industry to transport fluids, including highly caustic fluids. It is essential that these valves do not cause quiescent or dead spots in the fluid flow course which could cause the fluid to become stagnant and degrade or could trap solids resulting in the contamination of the fluid. In addition, it is important that the number of potential leakage sources or seals be kept to a minimum due to the highly caustic fluids often used in the semiconductor industry.
These valves must be made of materials highly resistant to the caustic fluids. Contact with metal parts is generally to be avoided. The components which contact the fluids are typically formed of fluoropolymers such as perfluoroalkoxy (PFA), polyvinylidene (PVDF), or polytetrafluoroethylene (PTFE).
3-way valves, such as the Galtek(copyright) valve produced by Entegris, Inc., Chaska, Minn., utilize a valve stem which operates within a flow channel portion of a valve body to control the flow of fluid between a common port and two other ports. These prior art designs utilize valve stems having multiple parts to allow the valve stem to be assembled within the flow channel portion of the valve body. As a result, the cost of manufacturing 3-way valves of this type is dependant upon to the number of components needed to form the valve stem and the steps involved in the assembly of the valve stem within the flow channel portion of the valve body.
There is a need for a 3-way valve utilizing a valve stem having a reduced or minimum number of non-integral components which can be quickly and easily manufactured and assembled within the flow channel portion with a minimal number of steps.
A 3-way valve comprising a molded fluoropolymer plastic valve body and a valve stem having integrally formed portions, the 3-way valve provides manufacturing advantages and is highly suitable for use with caustic fluids such as those used in semiconductor processing applications. Principal portions of the valve stem and valve body are integrally formed of plastic and are press-fit together minimizing the number of components, the number of joints between components, and the number of steps required to assemble the valve.
In a preferred embodiment, the valve body has a an upper portion containing a pneumatic actuation mechanism, an upper sealing portion, a central body portion, a lower sealing portion, and lower cap portion. The central body portion has a common port, a first port, a second port, all coplanar with one another, and a flow portion having a flow channel. The flow portion has a common port in flow communication with the flow channel, a first port in flow communication with the flow channel through the first valve seat, and a second port in flow communication with the flow channel through the second valve seat. The valve stem comprises an integrally formed fluid control portion in the shape of a figure eight with a first valve member for sealingly engaging the first valve seat, a second valve member for sealingly engaging the second valve seat, and a channel stem portion extending between the first and second valve members. The first and second valve members each having a larger width than the inner diameter of the flow channel. The valve stem may be press fit through the central body portion by deforming at least one of the flow portion of the body portion and the second valve member, resulting in the first valve member being operatively positioned adjacent to the first valve seat, the second valve member being operatively positioned adjacent the second valve seat, and the channel stem portion extending through the flow channel. The upper and lower sealing portions having contoured portions creating a contoured smooth fluid flow courses above and below the first and second valve seats.
The valve stem is moveable between a first position and a second position. In the first position, the first valve member sealingly engages the first valve seat and the second valve member is displaced from the second valve seat, thereby preventing the flow of fluid between the flow channel and the first port while allowing the flow of fluid between the flow channel and the second port. In the second position, the second valve member sealingly engages the second valve seat and the first valve member is displaced from the first valve seat, thereby preventing the flow of fluid between the flow channel and the second port while allowing the flow of fluid between the flow channel and the first port.
A feature and advantage of specific embodiments of the invention is that the valve stem is press-fit assembled within the valve body allowing the 3-way valve to be assembled quickly and efficiently. As a result, the 3-way valve is cheaper to manufacture than present 3-way valves.
Another feature and advantage of specific embodiments of the invention is that the valve stem utilizes a valve stem guide to assure proper alignment of the valve stem and the channel portion.
Yet another feature and advantage of specific embodiments of the invention is that it utilizes a single diaphragm to control the valve thereby reducing the number of components, reducing assembly costs, and allowing the valve to be made smaller than current 3-way valves.
Still yet another feature and advantage of specific embodiments of the invention is that the valve body may be molded rather than machined.
Another feature and advantage of specific embodiments of the invention is that the valve stem can be quickly and easily removed from the flow channel and replaced.
Further disclosure relating to plastic valves suitable for use in the semiconductor processing industry and for handling caustic fluids can be found in U.S. Pat. Nos. 5,335,696; 5,279,328; and U.S. application Ser. No. 08/843,456; now U.S. Pat. No. 5,924,441 all of which are assigned to the assignee of the instant invention. The two patents and the application are hereby incorporated by reference herein.